In geotechnical engineering applications, such as load bearing construction, erosion control and vegetation support, the engineering properties of the soil can have a significant influence on site reclamation and development operations, transportation infrastructure construction, and general construction costs and configurations. The components of the soil can influence the soil's load bearing capability, stability, resistance to lateral movement, drainage and settling characteristics. Desirable soil characteristics include high shear strength, low compressibility, good compactibility, high permeability, high ductility, low weight and high density.
In an attempt to improve soil properties, U.S. Pat. Nos. 4,790,691 and 4,867,614 disclose composite mixtures of natural soil selected from gravel, sand, silt and clay and about 0.1 to 5 percent by weight of a fiber additive including glass fibers, thermoplastic fibers and man-made fiber forming substances such as cellulosic and non-cellulosic or synthetic base materials.
Currently there is great interest in reclaiming waste materials for geotechnical applications. For example, Japanese Patent Application No. 55-124582 discloses a solidification method for waste matter in powdered form or waste matter in sludge form which is first dehydrated and dried to produce powdered waste matter. Examples of powdered waste matter disclosed include incineration ash, powdered waste matter from exhaust gas cleaning processes and powdered waste matter formed from sludge having inorganic substances as primary constituents, such as water supply sludge, plating sludge, slag and red mud. The powdered waste matter is mixed with a fibrous reinforcing material and, if necessary, a solidification accelerating agent, molded in the presence of a calcium constituent and solidified in a steam autoclave. However, this process involves costly drying of the waste materials and high pressure molding to produce a useable product. Processing of aqueous soil mixtures is not discussed.
In an existing commercial process, dredge material including sand, silt, organic material, trace metallic waste material and water is pumped from the floor of the ocean. The dredge material is mixed with lime or Portland cement in a pug mill to form a semi-solid soil material, which is then air-dried for about a week and used as soil for fill and building support applications.
It is desirable to enhance the physical properties of soils formed from aqueous soil mixtures such as dredge material for geotechnical engineering applications, to improve the processibility of such materials and to reduce the cost and/or time for drying such materials.